Cooking instructions

1. Preheat the oven to 180°C/160°C fan/Gas 4. Grease and line a 30 x 23cm cake tin with baking parchment.
2. Put the chocolate and butter into a large heatproof bowl set over a pan of gently simmering water (don’t let the bottom of the bowl touch the water underneath) and leave until melted, stirring occasionally (see Tips). 
3. Remove from the heat and cool the chocolate down by whisking in the sugars using a balloon whisk. Add the eggs and vanilla extract and mix in with a wooden spoon until combined. Sift over the flour and salt and stir again until smooth and combined. Pour into the prepared tin, smoothing the top level. 
4. Bake for 35–40 minutes, until cracked around the edges and soft in the middle (it will firm up as it cools), rotating the tin halfway through baking. 
5. If you are adding the chocolate chunks, take the brownie out of the oven after 20 minutes and vigorously throw the chunks of chocolate at the half-baked brownie so they break the surface. Return to the oven for the remaining cooking time. 
6. Transfer the brownie to a wire rack and leave it to cool in the tin, then cut into squares before serving. Once cooled, the brownies will keep in an airtight container for up to a week. Alternatively, cool the cooked brownie in the tin for 10 minutes, then cut into squares and serve warm with a dollop of thick cream.

Tip

If you prefer, put the chocolate and butter into a heatproof bowl, cover (leaving a small air gap) and melt in the microwave on high for about 3 minutes, stirring occasionally. These brownies also freeze well for up to a month. Simply wrap them tightly in cling film and freeze, then thaw at a cool room temperature before serving.